Yes, its usually not necessarily about sex, but that doesn't change the fact that if you remove the major testosterone-enducing organs that they're less likely to a)sexually assault, and b) commit violent crime. It also doesn't change the sexual nature of their crimes.

"if you cut off the mans johnson hes just going to kill" very unlikely. Removing the sexual organs does very distinct things to a person's biochemistry, among which are a lack of agression and a sharp decline in activity.

What about women rapists? Well, to start off, statistically, women comprise a very small minority of violent sex offenders (probably less than 5%, including the unreported incedents). That aside, they deserve the same treatment. Its just a matter of using an appropriate proceedure.

I have not been raped, but several people close to me have. The disrespectful and demeaning tone with which you approach this issue (albeit, perhaps completely internet ass-ness), is profoundly disturbing (assuming you're actually being frank).